Fibrous acoustical panel with impregnant in rear body portion



Aug. 1, 1967 R, SHANNON 3,333,656

FIBROUS ACOUSTIC/8L PANEL WITH IMPREGNANT IN REAR BODY PORTION Filed 001;. 29, 1964 i NVENTOR AWE/MPO F SHANNON 76 84 76 fig 76 United States Patent ware Filed Oct. 29, 1964, Ser. No. 407,323 4 Claims. (Cl. 181-33) This invention relates to panels for absorbing sound waves and blocking their transmission, said panels being composed of mineral fibers and impregnated, coated or both impregnated and coated with aninert, mineral material in particulate form.

This invention further pertains to acoustical panels resistant to high temperature and flames and to a method for producing such panels.

Also, this invention relates to an acoustical panel h-aving a stiff backing on the rear thereof providing supporting strength and protection against abuse.

The acoustical panels of this invention are particularly adapted for mounting in a suspended ceiling installation and to function as a barrier to high heat and flames. Panels of this invention also serve advantageously in other locations such as partitions and floors in which a reinforcing layer incorporated in the back side of the panel may provide structural strength as well as sound blocking properties.

The conventional acoustical panel of glass fibers eventually shrinks and becomes deformed under uncontrolled fire conditions. It sags or drops out of position when part of a suspended ceiling installation and thus fails to prevent or substantially retard the spread of a conflagration.

Attempts have been made to increase the fire retarding capacity of acoustical panels by fully saturating them with mineral particles. The products of these efforts have not been satisfactory due to the dusty effect of the saturant upon the faces of the panels. The powder loosens and drops sway under vibration and rubs off when contacted. In addition with full saturation, severe shrinkage has not been entirely avoided.

It is accordingly an object of this invention to provide an acoustical panel which is more dimensionally stable and form-retaining under high temperature conditions and possesses superior sound blocking characteristics.

Another object of the invention is to provide a panel which will remain in position in a suspended ceiling installation for at least two hours while its face surface is exposed to a hot flame at a temperature of 1850 F.

A specific object of the invention is to provide an acoustical panel of mineral fibers the rearv portion of which is impregnated with a stiffening mineral component and the exposed facing surface including perforations therein is free of sheddable particles.

A further object is an acoustical panel and a method of producing such apanel which has a main body of mineral fibers with a rear portion impregnated with a fire resisting mineral component in fine granular form and with a rear, more densified sealing coat of similar com- 7 position.

Another object of the invention is to provide a panel with an impregnating layer of inert mineral material in its rear portion which penetrates the panel adefinite predetermined distance. I

A still further object of the invention is to provide a panel with a sound blocking and reinforcing layer of mineral material on its rear facing.

Another object of the invention is to provide an acoustical panel which has a reinforcing, substantially impervious coating on its rear face which serves to block ice sound transmission therethrough and to integrate the panel for resistance to hot flames.

-An additional object is a method of producing a fibrous panel with a back portion blocking sound transmission therethrough.

A further object is a fibrous panel with sound blocking rear and edge portions.

An additional object of the invention is to provide a ceiling panel of mineral fibers which has kerfs along its edges for receipt of flanges of supporting bars and has a strengthening, particulate mineral material extending into the panel from the back side thereof to the level of the lower walls of the kerfs in the edges of the panel.

These and other objects and advantages of the invention are attained primarily by creating a continuous compressed web of bonded mineral fibers, splitting the web into panel blanks, applying over the upper surface of the blanks a slurry of fine mineral particles, said slurry having suflicient fluidity to soak into the blanks to a predetermined level. The practice of one phase of the invention also includes the application of an additional amount of a slurry of fine mineral particles to the upper surface of the blanks and thereby establish a heavier amount of the mineral particles in the upper surface area.

The invention and its objects and advantages will become more apparent in the following description with reference given to the accompanying drawings in which:

FIGURE 1 is an elevational view of a section of a production line including apparatus for practicing the invention;

FIGURE 2 is a plan view of a tus of FIGURE 1;

FIGURE 3 is a plan view of a broken away portion of a modified form of apparatus adapted for the practice of this invention;

FIGURE 4 is another plan view of a further modified form of apparatus, with portions broken away, adapted for practicing the invention;

FIGURE 5 is a vertical section with portions broken away of ceiling panels of this invention mounted on hanger barsof inverted T cross section;

FIGURE 6 is a similar vertical section of ceiling panels with kerfs in edge portions for receiving the flanges of supporting hanger bars; and 7 FIGURE 7 is a perspective view of a portable rack on which ceiling panels are carried into a drying oven.

In this disclosure ceiling panels is intended as a general term while those panels of greater planar dimensions and which are supported by hanger elements which abut the marginal portions of the facing or underside of the boards, Willfibe referred to as ceiling boards. The term ceiling tiles identifies smaller panels which are kerfed at their edges for reception of flanges of the hanger elements. In this arrangement the hangers are concealed. This diflerentiation, while arbitary (for instance ceiling tiles is a common term for small ceiling panels whether or not kerfed) is considered desirable as the practice of the invention may vary according to which design of panel is involved. The acoustical properties and the reinforced backing of the ceiling boards of this invention make these panels also suitable for form boards, roof deck, flooring and partitions.

In order to provide panels of fibrous glass which stand up under severe heat and fire conditions, the fibers should have an especially high softening leveLThe fire resisting properties of commercial glass fibers may be improved by application to the fibers of particles of toughening, de vitrifying and viscosity increasing agents such as titania, silica, alumina and asbestine. Fibers so treated are utilized in the panels of this invention.

In FIGURE 1 is shown a production line in which acoustical ceiling boards are 'being treated with a back portion of the apparaapplication of mineral particles. As indicated therein, panel blanks are received from a conveyor 12 preferably directly from blank producing apparatus including a fiber forming and collection station, a compressing pair of conveyer flights carrying the continuous mat of collected fibers through a binder curing oven, a surface sanding operation and transverse slicing means to cut the cured mat into blanks.

The density of these base panels or blanks of bonded fibrous glass may for example be approximately twelve pounds per cubic foot with an organic binder content of twelve percent by Weight. However, the density may reside in the broad range from three to twenty five pounds and the binder content run from five to forty percent.

As the panel blanks 10 travel along the conveyer 14 they receive on their rear sides, which usually have been lightly sanded and are here facing upwardly, a layer of impregnating material 22. This is in slurry form and flows from the weir 16. A constant flow from the weir is maintained by a continuous supply of the material arriving at the weir through piping 18. The material is spread in an even layer by the inclined flat chute 20.

The impregnating or filler material is of comparatively inert composition, preferably completely or predominantly of a mineral nature. Various materials including silicas and clays may be utilized. An example of a satisfactory formula has solid components of potassium silicate in the amount of sixteen percent by weight, forty-two percent of ball clay, and forty-two percent of colloidal silica. These ingredients are dispersed in water, with the latter constituting thirty percent by weight of the resulting slurry. The amount of water varies with the fluidity desired and the available drying facilities and may run over fifty percent. The slurry composition should not include ingredients which expand or contract on drying to an extent to cause warping of a panel impregnated or coated therewith.

To facilitate penetration and even distribution there may be need of fractional percentages of additives such as a wetting agent, a viscosity lowering ingredient, and an anti-forming agent. To effect a more complete sealing action effective for sound blocking by the applied layer of slurry a minor amount of a film forming element may be added to the mixture. Examples of organic film formers are methyl celluloses and vegetable gums. For sound blocking purposes the sealing layer should be applied to the edges as well as the back of the panel.

The impregnating material soaks into the interior of the fibrous blanks to a depth determined by the porosity of the fibrous mass, the size and shape of the slurry particles and the fluidity of the slurry, facilitated if desired by air drawn at an effectual velocity into the suction chamber 23.

The last portion of the slurry remaining on the surface of the blanks is wiped evenly across the blanks by the reciprocating brush 24, having bristles about one inch in length. The brush holder 25 rides in a guide 26. The brush may be approximately one and one half inches thick and be of a length to extend across the full width of the conveyer. A reciprocating stroke eight inches in length with a frequency of seventy strokes per minute has proved satisfactory.

About fifty ounces of the solid content of the slurry in this instance is spread over the back of a panel having nominal planar dimensions of 24 by 48 inches and intended to serve as a ceiling board supported directly along the edges of its exposed face by hanger bars. This amounts to one ounce of the solids applied to approximately twenty three square inches of the rear surface of such a panel. This single application of material is generally sufficient for ceiling boards for fire and high heat resistance.

While fifty ounces of the solids is presently preferred for incorporation in the back of one example of ceiling board with the cited dimensions, protection of a more limited nature against fire and heat may be secured with as little as twenty five ounces of the material. For sound blocking properties a still lower quantity of material may be used in forming a tight back and edge sealing layer.

A final sealing coat of material may be deposited upon the upper surface of the panels blanks by the sprinkler pipe 28, particularly if they are intended for acoustical tiles. This material 30 applied in an amount depositing only five ounces of solids over an area of 24 by 48 inches is formulated so as not to so easily enter the body of the blank but to remain on or adjacent the surface thereof.

Uniform distribution is secured through the action of a second reciprocating brush 32. The holder 33 of this brush rides in a guide 34. The application of the slurry 22 from weir 16 and the slurry '30 from the pipe 28 in this example results in a total of fifty-five ounces of mineral particles being deposited for penetration into the rear surface of each panel having planar dimensions of 24 by 48 inches.

The movement of the two brushes 24 and 32 is derived from motor 36. A rotating disc 38 is driven by the motor, as shown in FIGURE 2. A connecting rod 40 is mounted at one end to an eccentric pin 41 projecting from disc 38. The other end of the connecting rod is joined to the pivoting arm 44 which turns on the pivot pin 46. The ends of the brush holder 25 and 33 are reciprocated by the pivoting action of arm 44 to which they are both connected.

The action of the brushes in some manner not completely understood consolidates the portion of the impregnating material disposed upon and adjacent to the upper surface of the panels. It is apparently a fiber spreading and light ramming action. If not so brushed the filler or impregnant has an objectionable porosity which not only permits too great a transmission of sound through the panels but which also detracts from the reinforcing strength available from the mineral impregnant.

A microscopic study of an unbrushed coating of slurry frequently reveals the presence of tiny bubbles. These may be due to an inherent frothing of the slurry, air caught beneath the curtain of slurry, resistance to wetting by the mineral fibers, or to a combination of such or other factors. The brushing appears to disperse any such bubbles and to thus produce a more complete sealing layer of the mineral particles.

The consolidation of the surface material into a fairly impervious layer is also promoted by turning over the panels after they have been back coated and before the coating has been dried. This reversal is indicated by the arrows immediately preceding the oven 48 of FIGURE 1. Any further penetration of the slurry into the body of the panel is thus curtailed and a floiw of the slurry back toward the surface is induced. With this procedure the layer of mineral particles imbedded in the surface fibers may be restricted to a compact thickness of three thirty seconds of an inch.

As discharged from the oven 48 the panels 50 carry the coating 51 on their lower faces. The panels are then loaded on a pallet 52 for transfer to subsequent treating or packlaging stations. Instead of being moved through the drying oven 48 the panels 50, as shown in FIGURE 7, may be laid in reversed position on the cross bars 88 of a hand truck 90, the latter being then placed in a drying oven.

Instead of narrow brushes such as 24 and 32 illustrated in FIGURES 1 and 2, rollers 54, as shown in FIGURE 3, covered with bristles, nap or pile fabric, or sponge material may serve in consolidating the surface layer of mineral particles. The rollers are mounted for rotary movement within frames 56 and 58, which are reciprocated in the same manner as brushes 24 and 32 through a connecting rod 40 and an arm 44 pivoted on pin 46.

Another arrangement with aligned rollers 60 in frames 62 and 64 is illustrated in FIGURE 4. Other means such as broad rotary brushes and flexible wiping blades may be used to accomplish the spreading and sealing of the mineral coating.

When fire stopping panels intended for acoustical ceiling tiles with subsequently kerfed edges for receipt of hanger flanges are processed on the equipment of FIG- URES 1 and 2, deep penetration of the saturant of mineral particles is desired. The suction chamber 23 is then actuated to help draw the slurry from the weir 16 down into the panels.

Additional slurry 30 is then deposited by the sprinkler pipe 28. Such extra material is required to provide a rear sealing coat, consolidated by brush 32, with the slurry from the weir 16 drawn deply into the panels, the mineral particles are deposited in a somewhat porous or dispersed relation.

The fluidity of the slurry, particle size and shape, and the degree of vacuum of suction chamber 23 are selected to cause the slurry to descend intothe panels to a predetermined point at least even with the lower walls of the kerfs to be later cut into the edges of the panels. The extra integrating strength under high temperature conditions provided by the mineral particles thus extends down to .a point beyond the flanges of the hangers to within one eighth ofan inch of the face of the panel, the region where planar splitting or delamination occurs when conventional kerfedceiling tiles are subjected to high temperature flames. The depth of penetration should be approximately three eighths, one half and five eighths of an inch respectively for panels one half, five eighths and three quarters inches thick.

In FIGURE 6 is'illustrated a portion of a suspended ceiling installation incorporating acoustical ceiling tiles 76 with kerfs 78 in their edges for receiving the flanges of hanger bars 80. These panels have the described impregnation of mineral particles extending down slightly below the kerfs 78 as indicated'by the terminating line 84.

The panels in addition have a substantially impervious back coating 86 provided by the slurry from sprinkler 2.8. In one example of the practice of this invention inconnection with ceiling tiles the deep penetration is secured with a slurry having a solid content of approximately fifty percent by weight, the entry of which into the body of the panels being facilitated by air drawn down through the panels into a suction chamber such as 23 shown in FIG- URE l. A reciprocating wiping member such as the brush 24 of the apparatus of FIGURE 1 also contributes to a minor degree to the entry of the slurry into the body of the panels. About sixty-four ounces of solid particles are thus introduced into the panels for a back surface area of eight square feet.

The back coating 86 of the acoustical tile 76 secured from the second deposit of slurry which is consolidated by a wiping device such as the brush 32 of FIGURE 1, is restricted to the surface area of the panels by slightly altering the composition of the slurry. Such composition alter- .ation may involve increasing the solid content, omitting a wetting agent or by the inclusion of fine mineral fibers or some other bulk providing constituent. In this instance suflicient slurry is applied to provide approximately nineteen ounces of solid mineral particles in a sealing layer for a surface area of approximately eight square feet. This is less than one third of the amount of material in the slurry from weir 16 with which the panel is saturated to the lower sides of the kerfs.

In FIGURE 5 is illustrated a portion of a suspended ceiling installation incorporating acoustical ceiling boards embodying this invention. Smaller acoustical tiles with unkerfed edges would present a similar appearance.

As shown, the edges of the boards rest upon the lateral flanges of the hangers 72, which are of inverted T cross section. The hangers 72 are suspended from elements of the permanent ceiling by Wires, straps or other suitable devices. The upper or rear side of the panels incorporate the consolidated layer 51 of mineral particles. This layer or coating may have a thickness of only of an inch and for the most part lies beneath the surface of the panel. It is therefore reinforce-d by fibers of the boards.

Laboratory tests have proved that such panels will maintain themselves in position for over two hours with flames at a temperature of 1850 F. directed against their lower or room-facing surfaces. This stability is of great value in restraining the spread of a fire arising in an area of a building beneath such panels.

Tests have also shown that these panels with the consolidated back coating have such a low porosity that in addition to their sound absorbing capacity they serve very satisfactorily in blocking sound transmission therethrough. The panels are accordingly adapted for installation in suspended ceilings above adjoining rooms, where it is desired to keep sounds from one room from passing up through the panels and over the partition separating the rooms into the next room. While a thinner back coating of mineral particles may be produced according to this invention and is effective in curtailing sound transmission, its strengthening effect for maintaining the panels in position under fire conditions is impaired.

For sound blocking purposes the layer of particles should be sufficiently compact that when air is passed through the coated panel by establishing a vacuum on one side thereof the pressure on the outlet side is preferably that indicated by a measurement Well abovesixteen inches in an air pressure measuring water column. However, quite satisfactory performance in this regard is assured if the coating is sufliciently consolidated by wiping and by reversing the position of the panel immediately after it is wiped that the pressure measurement is as low as sixteen inches in a water column.

Mineral material in an amount between forty-five and fifty-five ounces for every eight square feet of panel surface area has been found to serve satisfactorily for ceiling boards from both a fire retarding and sound blocking standpoint. Where deep penetration is also requiredparticularly for ceiling tiles the amount of mineral material is increased to as much as ninety ounces for an area of eight square feet.

Where maximum protection against the spreading of a fire is not required and sound transmission loss is the main consideration the back coating may contain considerably less than forty five ounces of mineral material for eight square feet, the minimum limit of the specified recommended range, and be of a thickness from only one thirty second to three thirty seconds of an inch. However, the accompanying reduction in weight lowers the sound blocking capacity of the layer.

To prevent sound energy traveling angularly into the borders of panels and laterally upwardly from the edges of the panels, the edge surfaces should also be sealed. The same sound blocking mineral composition may be applied to the edges by a roller or spray nozzle.

A comparatively heavy sound blocking layer imbedded in the rear surface of a panel is a strengthening factor providing resistance to blows and loads and is of special benefit when the panel is used as part of a wall or floor structure.

While panels of fibrous glass are considered superior for the practice of this invention, panels of other mineral fibers such as asbestos, slag and aluminum silicate are also adapted therefor.

Some clays are well suited as ingredients for the backcoating and impregnant materials because their fine grained nature facilitates penetration and consolidation. A combination of different clays and silicas providing various granule sizes and different characteristics in respect to dispersion, coalescence, plasticity, Weight, sealing ability, low expansion or contraction, and water aflinity contribute to the desired functioning of the materials. Formulations, accordingly, may vary to a wide degree and still serve the purposes of the invention.

As previously indicated, precise control of depth of penetration into a panel is secured through selection of the ingredients, the amount of water in the slurry, the degree of air suction, and reversal of position of the panel before the material has dried, all balanced with the porosity and wettability of the fibrous body of the panel.

It will beunderstood that various changes or modifications may be made in the panels and methods described herein by those skilled in the art without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. An acoustical panel having a body of bonded mineral fibers, kerfs in the side edges of the panel for receiving hanger elements, a fire resisting impregnant of mineral material in particulate form extending down into the panel from the rear side thereof past the kerfs in the edges but extending short of the front side of the panel, said impregnant having sufficient stiffening effect to hold the body of bonded mineral fibers against deformation under high heat.

2. An acoustical panel having a body of bonded fibrous glass, kerfs in the side edges of the panel for receiving hanger elements, a fire resisting impregnant of mineral material in particulate form extending down into the panel from the rear side thereof past the kerfs in the edges but extending short of the front side of the panel, said impregnant having sufficient stiffening effect to hold the body of bonded mineral fibers against deformation under high heat. 11:4

3. An acoustical panel having a body'of bonded mineral fibers, kerfs in the side edges of the panel for receiving hanger elements, a fire resisting impregnant of mineral material in particulate form extending down into the panel from the rear side thereof past the kerfs in the edges but extending short of the front side of the panel, said impregnant having sufficient stiffening effect to hold the body of bonded mineral fibers against deformation under high heat, a layer of said mineral material on the rear side of said panel being consolidated into a more compact and impervious state than the balance of said mineral material within the panel.

4. An acoustical panel having a body of bonded mineral fibers, kerfs in the side edges of the panel for receiving hanger elements, a fire resisting impregnant of mineral material in particulate form extending down into the panel from the rear side thereof past the kerfs in the edges but extending short of the front side of the panel, said impregnant having sufficient stiffening effect to hold the body of bonded mineral fibers against deformation for a period of tWo hours with flames at a temperature of 1850 F. directed against the front or room facing side of the panel.

References Cited UNITED STATES PATENTS 1,568,415 1/1926 Pilliod 117-126 1,941,769 1/1934 Ward 1'81-33.1 1,950,420 3/ 1934 Stitt 18133.1 2,004,686 6/1935 Birchy 18133.1 2,785,099 5/1957 Holtsford 181-3311 2,787,723 4/ 1957 Fehr et al "117-126 2,946,158 7/1960 Seipt 181-331 3,009,829 11/1961 Gouveia 117-126 3,015,626 1/1962 Kingsbury 181-33.11 3,017,318 1/1962 Labino et al 117-126 3,077,413 2/1963 Campbell 117-126 3,103,444 9/ 1963 Cotts 181-33.1 3,111,188 11/1963 Rees et al. 18l-33.1 3,246,063 4/1966 Podgurski 181-3311 FOREIGN PATENTS 686,876 5/ 1964 Canada. 390,189 3/ 1933 Great Britain.

RICHARD B. WILKINSON, Primary Examiner.

R. S. WARD, Assistant Examiner. 

1. AN ACOUSTICAL PANEL HAVING A BODY OF BONDED MINERAL FIBERS, KERFS IN THE SIDE EDGES OF THE PANEL FOR RECEIVING HANGER ELEMENTS, A FIRE RESISTING IMPREGNANT OF MINERAL MATERIAL IN PARTICULATE FORM EXTENDING DOWN INTO THE PANEL FROM THE REAR SIDE THEREOF PAST THE KERFS IN THE EDGES BUT EXTENDING SHORT OF THE FRONT SIDE OF THE PANEL, SAID IMPREGNANT HAVING SUFFICIENT STIFFENING EFFECT TO HOLD THE BODY OF BONDED MINERAL FIBERS AGAINST DEFORMATION UNDER HIGH HEAT. 